Endocardial Implantation of a Cardioverter-Defibrillator in a 13-Month-Old Child Affected by Long-QT Syndrome and Syndactyly
A 13-month-old child with the uncommon variant of long-QT syndrome associated with syndactyly of feet and hands experienced an apparently life-threatening event during full-dose β-blocker therapy. The indication for an implantable cardioverter-defibrillator (ICD) was established, and the patient was admitted to the hospital. The QTc interval was 580 ms, and no mutations were present in any of the known LQTS genes. The child weighed 11.9 kg with a length of 76 cm. To minimize the surgical injury and reduce the potential risk of infection, a minimally invasive endocardial approach was developed.
We previously reported a novel transvenous endocardial implantation technique in children in whom we left a redundant loop of a defibrillation lead (screw-in; 9.3F) within the inferior vena cava (IVC) to allow further growth.1 This approach has been used successfully at our center in >15 children. In the present case, because of the age and weight of the little patient, the veins and the heart were too small to allow a 9.3F catheter to be positioned in the right ventricular apex with a loop in the IVC. For this reason, a bipolar pacing lead (Medtronic 5076; 52 cm in length; screw-in; 6.1F) was positioned in the right ventricular apex for ventricular sensing and pacing with a loop in the IVC, while the defibrillation catheter (Medtronic 6937; 35 cm in length) was inserted subcutaneously in the left sixth intercostal space. The two leads were tunneled (beneath the diaphragm) and connected to a generator placed beneath the rectus muscle (Medtronic GEM II VR 7229 CX) (Figure 1).
The defibrillation wavefront was from the defibrillation lead, positioned posteriorly in the left hemithorax, to the active can of the defibrillator, placed anteriorly in the left portion of the abdomen, embracing the little heart. At implantation, adequate pacing threshold (0.5 V at 0.5 ms) and sensing values (8 mV) were obtained. A single 12-J defibrillation impulse was able to interrupt the induced ventricular fibrillation.
The little patient was discharged without any complication after 6 days. An appropriate ICD shock occurred on sustained fast polymorphic ventricular tachycardia after 10 months and successfully terminated the arrhythmic episode (Figure 2).
To our knowledge, this is the first report of a cardioverter-defibrillator implantation in such a small child with a minimally invasive endocardial approach.